3 files changed, 32 insertions, 12 deletions
diff --git a/src/Data/Digest/Internal.chs b/src/Data/Digest/Internal.chs
index ed4e09e..86cea65 100644
--- a/src/Data/Digest/Internal.chs
+++ b/src/Data/Digest/Internal.chs
@@ -16,7 +16,6 @@
 
 module Data.Digest.Internal where
 
-import Control.Exception (assert)
 import Data.Bits (Bits((.&.)), shiftR)
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as ByteString
@@ -27,12 +26,13 @@ import Data.Word (Word8)
 import Foreign
        (FinalizerPtr, ForeignPtr, Ptr, Storable(alignment, peek, sizeOf),
         addForeignPtrFinalizer, alloca, allocaArray, mallocForeignPtr,
-        nullPtr, throwIf_, withForeignPtr)
+        nullPtr, withForeignPtr)
 import Foreign.C.Types
 import Foreign.Marshal.Unsafe (unsafeLocalState)
 import Unsafe.Coerce (unsafeCoerce)
 
 import Foreign.Ptr.Cast (asVoidPtr)
+import Result
 
 type LazyByteString = ByteString.Lazy.ByteString
 
@@ -70,11 +70,6 @@ evpMaxMdSize = {#const EVP_MAX_MD_SIZE#}
 -- Some of these functions return 'CInt' even though they can never fail. Wrap
 -- them to prevent warnings.
 
-alwaysSucceeds :: IO CInt -> IO ()
-alwaysSucceeds f = do
-  r <- f
-  assert (r == 1) (return ())
-
 evpDigestUpdate :: Ptr EvpMdCtx -> Ptr a -> CULong -> IO ()
 evpDigestUpdate ctx md bytes =
   alwaysSucceeds $ {#call EVP_DigestUpdate as ^#} ctx (asVoidPtr md) bytes
@@ -85,9 +80,6 @@ evpDigestFinalEx ctx mdOut outSize =
 
 -- Convert functions that can in fact fail to throw exceptions instead.
 
-requireSuccess :: IO CInt -> IO ()
-requireSuccess f = throwIf_ (/= 1) (const "BoringSSL failure") f
-
 evpDigestInitEx :: Ptr EvpMdCtx -> Ptr EvpMd -> Ptr Engine -> IO ()
 evpDigestInitEx ctx md engine =
   requireSuccess $ {#call EVP_DigestInit_ex as ^#} ctx md engine
diff --git a/src/Data/Hmac.chs b/src/Data/Hmac.chs
index 7ee68d2..907c352 100644
--- a/src/Data/Hmac.chs
+++ b/src/Data/Hmac.chs
@@ -33,10 +33,11 @@ import Foreign.Marshal.Unsafe (unsafeLocalState)
 import Unsafe.Coerce (unsafeCoerce)
 
 {#import Data.Digest.Internal#}
-       (Algorithm(Algorithm), Digest(Digest), Engine, EvpMd,
-        alwaysSucceeds, evpMaxMdSize, noEngine, requireSuccess)
+       (Algorithm(Algorithm), Digest(Digest), Engine, EvpMd, evpMaxMdSize,
+        noEngine)
 import Foreign.Ptr.Cast (asVoidPtr)
 {#import Foreign.Ptr.ConstantTimeEquals#} (constantTimeEquals)
+import Result
 
 type LazyByteString = ByteString.Lazy.ByteString
 
diff --git a/src/Result.hs b/src/Result.hs
new file mode 100644
index 0000000..dfd3b9f
--- /dev/null
+++ b/src/Result.hs
@@ -0,0 +1,27 @@
+-- Copyright 2018 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License"); you may not
+-- use this file except in compliance with the License. You may obtain a copy of
+-- the License at
+--
+--     https://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+-- License for the specific language governing permissions and limitations under
+-- the License.
+
+module Result where
+
+import Control.Exception (assert)
+import Foreign (throwIf_)
+import Foreign.C.Types
+
+alwaysSucceeds :: IO CInt -> IO ()
+alwaysSucceeds f = do
+  r <- f
+  assert (r == 1) (return ())
+
+requireSuccess :: IO CInt -> IO ()
+requireSuccess f = throwIf_ (/= 1) (const "BoringSSL failure") f